RNA polymerase I is an enzyme found in the cells of eukaryotes, responsible for synthesizing ribosomal RNA (rRNA). This type of RNA is a crucial component of ribosomes, the cellular machinery that translates messenger RNA (mRNA) into proteins. RNA polymerase I operates in the nucleolus, a specialized region within the nucleus where ribosome assembly begins. The enzyme recognizes specific DNA sequences called promoters, which signal the start of rRNA gene transcription. Once bound to the promoter, RNA polymerase I unwinds the DNA and synthesizes a complementary RNA strand. This process is essential for producing the rRNA needed for protein synthesis and overall cell function.